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Carbohydrates

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Title: Carbohydrates


1
Carbohydrates
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Reducing sugars
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Modified monosaccharides
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Glycosides
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Disaccharides
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Glycogen
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Polysaccharides
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Glycosaminoglycans
Proteoglycans lubricants and structural
components of connective tissues, mediate
adhesion of cells and bind cell proliferation
factors
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Biosynthesis of glycosides - glycosyltransferases
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Structure of A, B and O oligosaccharide antigens
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Glycoproteins
Components of cell membranes
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N-linked oligosaccharides
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Elastase, sectered glycoprotein (protease)
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Assembly of oligosaccharide procursors fro
dolichol donors in Endoplasmatic retuculum
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Lectins - carbohydrate-binding proteins Facilitate
cell- cell contact
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Carbohydrade Recognition at Infection Site
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                       Development of
carbohydrate-based vaccines
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Metabolism of carbohydrates
Glycogen
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Glycogen phosphorylase
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a-1,6-Glucosidase
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Glycogen phosphorylase
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Glycolysis
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Phosphoglucose isomerase
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Mechanism of triose phosphate isomerase
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Structure of glyceraldehyde 3-phosphate
dehydrogenase
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Mechanism of glyceraldehyde 3-phosphate
dehydrogenase
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Diverse fates of pyruvate
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Active site of alcohol dehydrogenase
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NAD binding site of dehydrogenases
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Gluconeogenesis
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Pyruvate dehydrogenase complex (irreversible
reaction)
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Citrate synthase
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Mechanism of Citrate synthase
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Aconitase
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Isocitrate dehydrogenase
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a-Ketoglutarate dehydrogenase
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Succinyl CoA synthetase
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Succinate dehydrogenase
Malate dehydrogenase
Fumarase
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Chemical and enzymatic syntheses of glycosides
and oligosaccharides
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Most commonly used protecting groups in
carbohydrate chemistry
66
Nucleophilic substitution of halogenases
(Koenigs-Knorr)
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Neighbouring group participation
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Trichloroacetimidate method
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                                        Scheme 1.
(a) CH3COCl, CH2Cl2, Pyridine (b) TMSOTf,
CH2Cl2, -10 C to room temperature (dry) (c) 90
TFA then BzClPyridine (d) 2 CH3COClCH3OH,
0 C to room temperature (e) PdCl2, 90 acetic
acidNaOAc, room temperature, 12 h then Cl3CN,
DBU, CH2Cl2 2 h (f) saturated NH3MeOH, room
temperature, 36 h then H2O, room temperature, 5
h.
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Thioglycoside/fluoride method
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Scheme 2. a) Ac2O/pyridine (quant.) b)
chloroacetic anhydride/pyridine, CH2Cl2 (93 )
c) HF/pyridine, NBS, CH2Cl2 (93  6), (96  7)
d) TMS-N3, BF3 OEt2, CH2Cl2 (91  8), (92  9)
e) MeOH, dioxane, NaOMe (67 ) f) K2CO3, MeOH,
CH2Cl2 (92 ) g) BF3 OEt2, CH2Cl2 (83 ) h)
BF3 OEt2, CH2Cl2 (86 ) i) K2CO3, MeOH, dioxane
(79 ) k) K2CO3, MeOH, CH2Cl2 (94 ).
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Reagents and conditions (a) NIS, TMSOTf 89.1
for 4 65.5 for 15 (b) 90 TFA 84.5 for 5
63.7 for 6 (from 1) (c) TMSOTf, CH2Cl2, 71.9
for 8 71.2 for 13 (d) Ac2O, Pyr (e) CAN,
343 Toluene MeCNwater (f) Cl3CCN, DBU, 78.7
from 9.
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Phosphite method
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Polymer supported synthesis
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Enzymatic methods
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Enzymatic synthesis with glycosynthases (mutated
glycosidases lacking nucleophile)
Synthesis of hexasaccharides 1 and 2 by route 1.
i), ii) phosphate buffer pH 7.0, CaCl2 0.1 mM,
35 C iii) Ac2O/pyridine, 24 h, RT (80  from
3) iv) MeONa/MeOH, 4 h, RT (90 ) v) 1 M HCl,
30 min, RT vi) Ac2O/pyridine, 12 h, RT (75 
from 4) (vii) MeONa/MeOH, 3 h, RT (90 ).
79
Wong, Ley
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